In the interests of fuel economy, there is an increasing drive within the automotive industry towards weight reduction of the component parts of vehicles. However, the weight reduction needs to be achieved without compromising the necessary strength or robustness of the components and, preferably, without increasing material costs or manufacturing costs.
A vehicle wheel bearing is an example of an automotive component where weight reduction is desirable, also in view of the fact that the wheel bearings belong to the unsprung weight of a vehicle. Raceways of the bearings need to be made from a material of sufficient hardness in order to withstand the stresses of rolling contact. Titanium and certain ceramics are materials that possess the necessary mechanical properties and are also low in weight. They are also expensive and, consequently, bearing steel is more commonly used. Bearing steel has excellent hardenability but cannot be viewed as a lightweight material. Thus, one solution for obtaining a wheel bearing that is relatively cheap to manufacture and reduced in weight is to form the bearing rings from bearing steel and to form further structural elements of the wheel bearing from a lightweight material.
In SE530892, a bearing unit is suggested that has inner and outer bearing rings made from first and second materials. The first material of the bearing rings can be a bearing steel, which serves as raceways for rolling elements, and the second material is joined to the first material by a semi-solid metal process. The second material can be a lightweight metal in order to maximise the potential for weight reduction.
There is still room for improvement, however, in terms of realizing a lightweight bearing unit that is capable of delivering the same mechanical and structural performance as a conventional unit made entirely from e.g. a bearing steel.